Cool an attic during hot weather

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gegyx
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Cool an attic during hot weather




by gegyx » 20/05/22, 00:51

Cool an attic during hot weather

I'm in an ordinary house with a sloping double roof, covered only by fiber cement slates, which have always been waterproof for 53 years.
No insulation under the frame.
20cm glass wool above the living floor.

So a large attic, full to bursting, with bulky objects judiciously placed on the rafters.
In summers, we suffer from the heat when it hits during the day.
In fact, the attic with its buffer inertia from the bazaar, becomes a bread oven...
And at night it is painful.
**
The green roof is not considered.
**
I had thought about remedying it, in an original way (in my opinion), well over 30 years ago, without ever doing it because I was always looking for the best way to achieve it.
**
It is simply a question of moistening the exterior roof, by variable interludes according to the temperature under the roof, and only, to avoid a 35° at night in the "habitable" / : Shock:
In a discreet way, that is to say not demonstratively, in the necessary proportion.
No question of putting a turnstile there.
Nor to spray water from the ground on a roof 7m higher (two levels below), every 20 minutes.

I was thinking of installing a pipe with small holes of 1mm every 1cm, eg.
Placed just at the height of the roof in order to water the 2 slopes with holes at an angle of 70°.
Thus it will flow on the slopes, until the entire surface is wet, then stop on pause.
And evaporation will do its job to cool the surface.

I don't claim to cool the house like this, just prevent the attic from overheating like a bread oven, during “heat waves”.
Water is not a problem as I have a rainwater tank.

Of course we will criticize the expense of water, but it's just to be able to sleep in a room at less than 30°.
We just had a week, which reminded me of this problem, recurring in the summer and less bearable with age.
I think that this “wastage” for an outside view (and yet so useful for us) is much less than buying an air conditioning unit and supplying it with electricity all day… It's clear.
**
For the realization, I was thinking of a copper pipe (over 13m), so that it remains permanent, but corrosion and verdigris on the holes? (It's still useful for mosses, but hey, it's been fine for half a century now)

But I fear for the weakening of the flow for the far holes.
I imagine that rather than feeding it in 2 places, to only make a water inlet in the middle of the 13m.
On 6,5 m the flow would remain correct?
***
What do you think ?
And technical opinions and advice from knowledgeable do-it-yourselfers.
On the type of pipe.
If we shouldn't rather put one on each slope so as not to bother life, for the angulation of the holes.
And to avoid a possible adjustment, because my mobility on the roof, is not really there any more, to walk me briskly there.
This would allow them to be powered independently. Since the East-West slopes are exposed together only in the middle of the day.
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Re: Cool an attic during hot weather




by izentrop » 20/05/22, 01:51

gegyx wrote:20cm glass wool above the living floor.
So a large attic, full to bursting, with bulky objects judiciously placed on the rafters.
Is the glass wool above the suspended ceiling or between bastaings? and what type of floor in the attic?

I am thinking of thermal bridges and if the insulation is not sufficiently airtight?

If the roof is in good condition, there is the inexpensive solution of an (additional) insulation under the slope of the attic with hangers and fur, rain barrier and airtight membrane on the underside.
I was lucky when I did this in 2005 that the cost of the insulation was still deducted from taxes, without going through a craftsman.
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Ahmed
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Re: Cool an attic during hot weather




by Ahmed » 20/05/22, 08:09

Establishing natural ventilation (if possible) under this roof would limit the rise in temperature...
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Re: Cool an attic during hot weather




by humus » 20/05/22, 09:02

I don't know what it's worth, I have a bit the same problem (without the mess in the attic : Mrgreen: ) and I was thinking of putting some reflective insulation on the slopes to contain the radiation from the tiles, and adding insulation thickness to the attic floor.
All this being interesting in summer and winter.

Ahmed's idea of ​​ventilation seems to me three interesting too, I would have seen it mechanical. a fan consumes 60W.
At least it handles the emergency. Now you need a good opening for fresh air, which I don't have. : roll:
The evacuation is done by the tiles but the best would be an opening opposite the arrival.
And in addition maybe a fribro roof is more airtight?

A diameter of 10cm even with a fan seems insufficient for an attic and that's all I currently have.



Another tip to avoid overheating is to avoid hot topics on forum ! : Lol:
Last edited by humus the 20 / 05 / 22, 09: 12, 1 edited once.
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Ahmed
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Re: Cool an attic during hot weather




by Ahmed » 20/05/22, 09:10

Humus, you produced an annoying shell! : Mrgreen:
Yes, in my idea, it would take large opposing openings to create a sufficient air current... Ideally, openings in the lower parts and others in the upper parts in order to maintain a convective flow. However, this would only be relevant during the hot season.
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Re: Cool an attic during hot weather




by humus » 20/05/22, 09:14

It's better ? : Lol: (I took the time to find : Lol: )
Don't blindly trust machines (spell checker : Wink: )
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Re: Cool an attic during hot weather




by Christophe » 20/05/22, 09:16

Thin insulators work quite well against IR radiation...a simple survival blanket is enough!
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gegyx
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Re: Cool an attic during hot weather




by gegyx » 20/05/22, 10:51

And if not the shot of the free fleet to moisten the roof? :D
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Re: Cool an attic during hot weather




by Christophe » 20/05/22, 10:57

It will work but in the building it is always better to favor a passive solution than an active one...

Otherwise, bin install solar panels (PV or thermal) ... it will cool your roof!
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Re: Cool an attic during hot weather




by izentrop » 20/05/22, 11:04

Christophe wrote:Thin insulators work quite well against IR radiation...a simple survival blanket is enough!
Yeah, for the insulation will have to be ironed, especially in summer. You can just count on its vapor barrier side. Beware of condensation on the frames in winter. https://conseils-thermiques.org/contenu ... _mince.php
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